As Dictyostelium cells differentiate from the non-cohesive to the cohesive state, they synthesize two lectin-like carbohydrate binding proteins (CBP I and II) which have been implicated as primary components of the morphogenetic cell cohesion system. The proposed work will focus on structural features of these two molecules and on the nature of their association with the cell surface. Peptide mapping affinity chromatography, and immunochemical procedures will be employed to study the structural relationships between CBP I and II, and to identify structural and functional domains within the molecules. The nature of association of the CBP's with the cell surface, and the kinetic relationships between the intracellular and surface-localized CBP pools will be probed by application of specific labeling and immunochemical techniques both to wild type cells and to mutants showing altered topological distribution of the CBP's.